# # Program information file # PROGRAM_ID 2024A063 PROGRAM_TITLE Using iSHELL To Measure the Magnetic Field Strengths of Chemically Peculiar Ap/Bp Stars PROGRAM_INV1 Drew Chojnowski PROGRAM_INV2 Pamela Marcum PROGRAM_INV3 PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT stellar PROGRAM_ABSTRACT_BEG Chemically peculiar Ap/Bp stars are the most magnetic class of main sequence stars, and despite that, they remain very poorly understood despite more than 60 years of study. The primary mystery surrounding these stars deals with the origin of their global, and occasionally very strong [up to 34 kG] magnetic fields. Whereas the magnetic fields of low-mass stars are generated in surface convection zones, this should not be possible in the radiative envelopes of A- and B-type stars. Rather, the magnetic fields of Ap/Bp stars are fossil fields that were apparently built into the the stars at some earlier stage of stellar evolution or perhaps during binary mergers. The surface heavy metal enhancements and exceedingly slow rotation of these stars are linked to magnetism, but both traits have yet-to-be satisfactorily explained on a theoretical level. We propose to improve our statistical knowledge of the magnetic fields of Ap/Bp stars via use of the iSHELL instrument for follow-up of a large new sample of Ap/Bp stars being discovered by the SDSS/APOGEE survey. In particular, we aim to measure weak [<5 kG] magnetic fields that are hinted at in APOGEE spectra but that can only be measured via the Zeeman effect in NIR spectra of considerably higher resolution like those iSHELL can provide. We will also construct the first ever high-resolution NIR atlas of Ap/Bp stars to establish the heavy metal line content and better inform future NIR surveys. PROGRAM_ABSTRACT_END